Surgical intervention and grafting are sometimes necessary to restore mechanical function and reconstruct the morphology of bone resulting from trauma, tumors, or abnormal bone developments. Synthetic materials such as metals and bone cements have also been used for many years, but often result in stress-shielding to the surrounding bone and fatigue failure of the implant. Another possibility is autologous bone grafting, although the supply of autologous bone tissue is limited and its collection is painful, with the risk of infection, hemorrhage, cosmetic disability, nerve damage, and loss of bone function. In addition, significant morbidity is associated with autograft harvest sites. These problems may be overcome by engineering tissue using scaffolds made of synthetic or natural biomaterials that promote the adhesion, migration, proliferation, and differentiation of bone marrow stem cells, also known as mesenchymal stem cells (MSCs). An association between biocomponents and biologic regenerative and repair responses can be promoted by providing a scaffold containing spaces morphologically compatible with osteons and their vascular interconnections.
The immediate microenvironment and the three-dimensional (3D) organization are important factors in differentiation in general and particularly in osteogenic differentiation.
Some bone tissue engineering scaffolds consists of natural polymers, such as collagen, alginate, hyaluronic acid, and chitosan. Natural materials offer the advantages of specific cell interaction, easy seeding of cells because of their hydrophilic interactions, low toxicity and low chronic inflammatory response. However, these scaffolds often are mechanically unstable and do not readily contribute to the creation of tissue structures with a specific predefined shape for transplantation. To obtain mechanical strength, chemical modification is required, which may lead to toxicity.
While most candidate materials must be synthetically modified to meet the essential requirements of an adequate bone and/or cartilage substitute, this is not necessarily the case for Marine skeletal material, such as natural coral exoskeletons. Calcified sessile and free-living organisms harbor a wide array of nanoscale to mesoscale modularly organized skeletal materials.